Addressing Flood Risks: A Complete Strategy for Börwang

Teh Haldenwang municipal council has given the green light to a considerable flood protection project aimed at safeguarding the Börwang district. This decision follows extensive deliberations and revisions to initial plans, driven by updated flood event calculations. The approved plan focuses on managing water flow from the east,which has historically posed a significant challenge to the community.

The Genesis of the Project: Mitigating Water Runoff

The need for enhanced flood protection stems from the area’s geography, where significant water runoff from the eastern slopes converges towards Börwang. Compounding the issue, drainage systems installed approximately 15 years ago during the development of the Mühlenweide construction area have proven insufficient. The current flood control concept awaits formal approval under water law regulations.

A critical component of the project involves relocating an outlet structure within the “At the Mühlenbauer” construction zone. This open shaft currently serves as a drainage point during heavy rainfall. Mayor Josef Wölfle emphasized that relocating this structure is essential to prevent future flooding of building sites. The diverted water will then flow into the Börenbach stream, possibly impacting residents downstream towards Stielings, necessitating careful planning for rain retention.

Exploring Solutions: Retention Options and Cost Analysis

During a recent council meeting, Klaus Bäumler from engineering firm A&B presented several flood mitigation options. These proposals centered on managing the catchment area 2, which extends from the “an der Mühlenweide” construction area towards the north-east.

• Underground Storage (Solution 1): Utilizing buried storage boxes with a capacity of approximately 200 cubic meters.Estimated cost: €330,000 (excluding planning).
• Retention on Unsold building Site (Solution 2): Constructing a retention system on an available building plot. Estimated cost: €295,000.
• Open Pool (Solution 3): Creating an open retention pool on the building site. Estimated cost: €145,000.
• Dam Construction (Solution 4): Building a dam on the state road OA 12 at the Börenbach crossing. Estimated cost: €500,000.

Bäumler highlighted the maintenance challenges associated with closed systems (Solutions 1 and 2), noting that sediment and debris accumulation can lead to higher operating costs compared to an open system (Solution 3). However, closed systems offer the advantage of being concealed underground, allowing for surface landscaping.

Variant 4, the dam construction, represents the most comprehensive solution, addressing surface water from multiple catchment areas. This dam, standing two meters high at its lowest point, is designed to collect approximately 11,000 cubic meters of water. Planning costs, estimated at 15-17%, would be added to each solution.

Council Debate: Balancing Cost, Environmental Impact, and Long-Term Benefits

Council members engaged in a robust discussion, weighing the pros and cons of each option. Tobias Weizenhöfer questioned the necessity of dam construction, advocating for the preservation of natural storage capacity. He expressed concerns about the potential impact on agricultural land.

Bäumler countered that the dam, with its carefully designed slope, would be environmentally amiable and manageable. He cautioned against inaction, emphasizing the potential consequences of uncontrolled water flow. He also noted that constructing a larger basin in variant 3 could lead to increased maintenance due to terracing and embankment requirements.

Christian Holl, Ingo Schubert, Matthias Amann, and Michael Hauke voiced their support for the dam structure, emphasizing its long-term benefits. Hauke argued that the larger upfront investment would prove more cost-effective in the long run, potentially avoiding the need for future interventions in catchment area 3. He also noted the existing property exchange transactions related to the dam site.

Mayor Wölfle acknowledged the concerns of farmers potentially affected by the dam’s impact on water flow, assuring them of compensation.He presented the dam as a long-term investment, while also highlighting the possibility of implementing a smaller-scale flood protection measure in the short term. He also noted that pursuing the dam project later could benefit from potential funding opportunities, given the progress already made on approvals.

Unanimous Decision: Prioritizing Comprehensive Flood Protection

Ultimately, the Haldenwang local council unanimously voted in favor of the dam construction, signaling a commitment to a comprehensive and enduring flood protection strategy for Börwang.